Split test site exclusions into own class

package_manager/package_manager.services.yml

@@ -128,6 +128,12 @@ services:
       - '@string_translation'
     tags:
       - { name: event_subscriber }
+  package_manager.test_site_excluder:
+    class: Drupal\package_manager\EventSubscriber\TestSiteExcluder
+    arguments:
+      - '@package_manager.path_locator'
+    tags:
+      - { name: event_subscriber }
   package_manager.excluded_paths_subscriber:
     class: Drupal\package_manager\EventSubscriber\ExcludedPathsSubscriber
     arguments:

package_manager/src/EventSubscriber/ExcludedPathsSubscriber.php

@@ -83,10 +83,6 @@ class ExcludedPathsSubscriber implements EventSubscriberInterface {
     // project root, and paths that are relative to the web root.
     $web = $project = [];
 
-    // Always ignore automated test directories. If they exist, they will be in
-    // the web root.
-    $web[] = 'sites/simpletest';
-
     // If the core-vendor-hardening plugin (used in the legacy-project template)
     // is present, it may have written security hardening files in the vendor
     // directory. They should always be ignored.

package_manager/src/EventSubscriber/TestSiteExcluder.php

+<?php
+
+namespace Drupal\package_manager\EventSubscriber;
+
+use Drupal\package_manager\Event\PreApplyEvent;
+use Drupal\package_manager\Event\PreCreateEvent;
+use Drupal\package_manager\Event\StageEvent;
+use Drupal\package_manager\PathLocator;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Excludes 'sites/simpletest' from staging operations.
+ */
+class TestSiteExcluder implements EventSubscriberInterface {
+
+  use PathExclusionsTrait;
+
+  /**
+   * Constructs a TestSiteExcluder object.
+   *
+   * @param \Drupal\package_manager\PathLocator $path_locator
+   *   The path locator service.
+   */
+  public function __construct(PathLocator $path_locator) {
+    $this->pathLocator = $path_locator;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    return [
+      PreCreateEvent::class => 'excludeTestSites',
+      PreApplyEvent::class => 'excludeTestSites',
+    ];
+  }
+
+  /**
+   * Excludes sites/simpletest from staging operations.
+   *
+   * @param \Drupal\package_manager\Event\StageEvent $event
+   *   The event object.
+   */
+  public function excludeTestSites(StageEvent $event): void {
+    // Always ignore automated test directories. If they exist, they will be in
+    // the web root.
+    $this->excludeInWebRoot($event, ['sites/simpletest']);
+  }
+
+}